By utilizing an imide compound such as N-hydroxyphthalimide and N-acetoxyphthalimide, a variety of reactions (e.g., oxidation with molecular oxygen, carboxylation, nitration, sulfonation, acylation, radical-coupling reaction) can be smoothly carried out under a mild condition.
For example, Japanese Patent Application Laid-Open No. 38909/1996 (JP-A-8-38909) and Japanese Patent Application Laid-Open No. 327626/1997 (JP-A-9-327626) disclose a process for oxidizing a substrate (e.g., a hydrocarbon, an alcohol) with a molecular oxygen in the presence of an imide compound such as N-hydroxyphthalimide, and if necessary, a metal co-catalyst to produce an alcohol, an aldehyde, a ketone, and a carboxylic acid corresponding to the substrate.
Moreover, Japanese Patent Application Laid-Open No. 278675/1997 (JP-A-9-278675) discloses a process for oxidizing a conjugate compound with the imide compound.
Japanese Patent Application Laid-Open No. 316610/1998 (JP-A-10-316610) discloses a process for oxidizing an ether in the presence of the imide compound to produce an ester, an acid anhydride, a lactone or the like. WO99/50204 discloses a process for oxidizing a compound having a non-aromatic ethylene bond with a molecular oxygen in the presence of the imide compound and a co-oxidizing agent to produce the corresponding epoxide, and a process for oxidizing a ketone with a molecular oxygen in the presence of the imide compound and a co-oxidizing agent to produce the corresponding ester or lactone.
Further, Japanese Patent Application Laid-Open No. 239730/1999 (JP-A-11-239730) discloses a process for reacting a substrate with a nitrogen oxide in the presence of the imide compound to obtain the corresponding nitro compound, and a process for reacting a substrate with carbon monoxide and oxygen in the presence of the imide compound to produce the corresponding carboxylic acid. WO99/41219 discloses that an acylation reaction proceeds under a mild condition by reacting a substrate with oxygen and a vicinal (adjacent) dicarbonyl compound (e.g., biacetyl) in the presence of the imide compound. Furthermore, the Lecture Draft of Spring Annual Meeting of Chemical Society of Japan (1999) reports that an α, β-unsaturated ester and an alcohol are reacted with oxygen in the presence of N-hydroxyphthalimide as a catalyst, thereby a radical-coupling reaction proceeds to form α-hydroxy-γ-butyrolactone with high yield. Moreover, the literature reports that a hydrocarbon such as an adamantane is reacted with oxygen and sulfur dioxide by using N-hydroxyphthalimide as a catalyst to form the corresponding sulfonic acid.
As mentioned above, the imide compound has been utilized as a catalyst for a wide variety of organic synthetic reactions. After utilizing the imide compound for a variety of reactions, there is proposed a process for separating a reaction product and the imide compound. For example, Japanese Patent Application Laid-Open No. 114702/1998 (JP-A-10-114702) discloses a process for separating a reaction product and an imide compound from a reaction mixture obtained by oxidizing a substrate in the presence of an oxidation catalyst (the imide compound). In this process, an aqueous solvent and a non-water-soluble solvent separable from the aqueous solvent are used to distribute the oxidation reaction product into a phase of the aqueous solvent and the imide catalyst into a phase of the non-water-soluble solvent, respectively. Therefore, the process is suitable for separating a water-soluble reaction product and a non-water-soluble catalyst, but it is difficult to separate a low-polar or non-water-soluble reaction product and a non-water-soluble catalyst. Further, in the process, it is sometimes difficult to separate a water-soluble product from an aqueous phase depending on the species of the oxidation reaction product. In particular, when a reaction is carried out in the coexistence of a metal catalyst in order to accelerate the reaction, it is difficult to separate the oxidation catalyst and the metal catalyst efficiently, as well as separating the reaction product. Therefore, it is difficult to separate, recover and reuse the metal catalyst.
Moreover, when the imide compound is utilized as a catalyst for various reactions, as the reaction proceeds, the imide compound changes into the corresponding N-non-substituted imide compound or N-substituted oxyimide compound in which a substrate is attached to oxygen atom adjacent to nitrogen atom (e.g., N-alkoxyimide compound) to deteriorate an catalytic activity considerably. In the case where such a catalyst which has been deactivated (hereinafter, sometimes referred to a deactivated catalyst) contaminates an article of the reaction product, there is a possibility that the quality of the article is deteriorated.
Further, a desired result cannot be arrived even when the deactivated catalyst is recycled to the reaction system without the specific treatment. Thus, as a method for regenerating the catalyst which has been deactivated, Japanese Patent Application Laid-Open No. 188265/1999 (JP-A-11-188265) discloses a process for treating the deactivated imide compound with a hydroxylamine or an acid. However, the process cannot still provide a satisfied regeneration yield of the imide-series catalyst.
It is, therefore, an object of the present invention to provide a process for efficiently separating a reaction product and an imide compound from the reaction mixture.
It is another object of the invention to provide a process for conveniently obtaining a reaction product with high purity.
A further object of the invention is to provide a process for efficiently separating an imide compound and a metal catalyst from a mixture containing the imide compound and the metal catalyst.
It is yet another object of the invention to provide a process for efficiently regenerating an imide compound which has been utilized in a reaction to be deactivated by a simple and convenient operation.